An ion exchange membrane, a separation membrane, uses the momentum of mass transfer as electromotive force in separating ionic materials. When cation exchange membrane systems supply current through anodes and cathodes, cations included in electrolyte solutions move to the cathode through ion exchange membranes, and anions cannot penetrate through the ion exchange membrane through the Donnan exclusion of cation exchange membranes. Likewise, anion exchange membrane systems enable anions included in the electrolyte solution to move to the anode through ion exchange membranes, and prevent cations from penetrating the ion exchange membrane by the Donnan exclusion of anion exchange membranes. In such a manner, ionic materials may be separated.
In the same way, when current is supplied while cation exchange membranes and anion exchange membranes are bonded to each other, such that cation exchange layers are oriented toward cathodes and anion exchange layers are oriented toward anodes, water molecules are decomposed into hydrogen ions (H+) and hydroxide ions (OH−) to move to the cathode and the anode, respectively, thus manufacturing acids or bases. This process may be applied in various types of chemical and biological processes.
Meanwhile, the water decomposition characteristics of bipolar membranes depend on the ion selectivity and membrane resistance of respective ion exchange membranes that form systems. When a degree of ion selectivity is low, a co-ion leakage phenomenon may cause a reduction in water decomposition efficiency (or current efficiency), and when a level of membrane resistance is high, water decomposition efficiency may be reduced at a constant potential. Bipolar ion exchange sheets have been produced by using a conventional method of producing a sheet using cation or anion exchange resin powders and polyethylene binders and coating a mixture having an opposite polarity thereon. Bipolar ion exchange sheets have good ion adsorption characteristics but low ion selectivity and high membrane resistance to reduce water decomposition efficiency. In order to regenerate bipolar ion exchange sheets, a high level of voltage is required to be applied thereto, which may cause the generation of heat.
Related Art Document: (Patent Document 1) Korean Patent Publication No. 2007-0052285